Air-circulation classifier



June 25, 1963 H. JAGER 3,095,369

AIR-CIRCULATION CLASSIFIER Filed June 14, 1961 L alggm ai wilt W MW i Q'JWMMIINI I r g u United States Patent 3,095,369 AIR-CIRCULATION CLASSIFIER Heinz Jiiger, Bochum-Riemke, Germany, assignor to Westfalia Dinnendahl Groppel Aktiengeseiischaft, Bochum, Germany, a corporation of Germany Filed June 14, 1.961, Ser. No. 117,087 6 Claims. (Cl. 209-139) My invention relates to air-circulation type classifiers for sorting coarse and fine fractions of solid material under the action of centrifugal force and entrainment by air. In a more particular aspect, my invention concerns classifiers in whose grading chamber the material to be classified is centrifugally distributed by a whirling plate and is subjected to a current of air travelling on a circulatory path. In such classifiers, the air currents, ascending helically, can entrain the dust to be separated to carry it out of the grading chamber, whereas the grits or other coarse constituents are centrifugally flung outwardly against the wall of the grading space. For maintaining a helical upward path of the air, the suction space at the top of the grading chamber in a known classifier of this type was given a spiral-shaped design resembling that used for air blowers; However, such classifiers, as a rule, have such a large diameter that the effect of the spiral-shaped suction space is only slight.

It is an object of my invention to improve the above mentioned classifiers towards a more efiective and more uniform rotation of the classifying air current.

To this end, and in accordance with a feature of my invention, the exhaustion of the dust-laden air at the top of the grading chamber is efiected by mean-s of two or more tangential suction conduits. The individual suction conduits may be connected to. a common conduit which leads to a blower and comprises a dust precipitator, such as a cyclone. However, according to another feature of my invention, each individual suction conduit is provided with its own, relatively small cyclone, and the various cyclones are preferably distributed about the classifier housing thus aifording a particularly compact, over-all construction of the classifier equipment.

According to another feature of my invention it is preferable to provide a guiding cone or guiding cylinder around the material-supply conduit of the classifier, the surface of the guiding structure being concentric to the inner wall of the grading chamber so that the chamber has a uniform cross-section along the chamber height. This secures a uniform loading of the suction conduits for a constant air velocity, and also a complete entrainment of the ascending classifier air on the desired spiral or helical path.

According to another feature of my invention, it is further preferable to make the height of the conical or cylindrical guide structure adjustable, together with the supply conduit and the whirling disc. This permits changing the height of the suction space during operation within the grading chamber, if desired.

The foregoing and more specific objects, advantages and features of my invention, said features being set forth with particularity in the claims annexed hereto, will be apparent from the following description of the embodiment of a classifier according to the invention illustrated by way of example on the accompanying drawing in which:

FIG. 1 is a vertical section through the classifier.

FIG. 2 shows schematically one-half of a cross section taken along line II-II in FIG. 1.

The illustrated classifier comprises a sheet-metal housing 1 which forms a grading chamber S in its upper portion. A supply conduit 2 protrudes from above, centrally into the grading chamber S and terminates above a whirling disc 3. The vertical shaft 3a of the disc 3 Patented June 25, 1963 is provided with a belt sheave 3b by mean-s of which the whirling disc can be driven from a suitable motor. The upper portion of the supply conduit 2 may be branched into two or more branches as shown. The upper portion 2:: of the supply conduit is telescopically surrounded by a lower portion 2b which can be lifted together with the part 4a of a guiding cone '4, by means of suspension rods 21 which carry respective wing nuts 22 in engagement with a fixed support 23. Another nut 24, threaded on the upper journal of the drive shaft 3a and resting on a fixed support 25, when being turned causes the whirling disc 3, together with the drive shaft 3a, to be adjusted to the desired height relative to the classifier housing '1. This adjusting nut 24 for vertical shaft 3a corresponds to those conventional and well known in the art, such as that illustrated in Patent No. 2,922,520 of Gustavsson et al. or on pages 35 or 99 of the book The Engineers Illustrated Thesaurus, by Herbert Herkimer, published in 1952 by Chemical Publishing Co., Inc. The supply conduit is coaxially surrounded. by the guiding cone 4 which has a telescopic lower portion 4a rigidly fastened to conduit portion 2b so as to be lowered or raised together therewith in the above-described manner. The angle of inclination of the guiding cone corresponds to that of the classifier wall that surrounds the grading chamber S. As a result the grading chamber has uniform. cross section as indicated in FIG. 1 by the constant distance a.

The grit particles separated in the grading chamber drop into the funnel shaped lower end 5 of the classifier and are discharged through an outlet conduit 6.

A circulating air blower 7 is mounted outside of the classifier proper and is connected therewith by circulatory air conduits. The classifier forces the air through an inlet conduit 8 into the classifier housing Where the air, after passing through an adjustable jalousy assembly 9, travels upwardly into the grading chamber. Connected to the top portion of the grading chamber S are a number of tangential suction conduits 10 which lead to respective cyclones 11 from which the clean air is sucked back to the blower 7 through a common return conduit 12. The dust separated in the cyclones 11 is collected in a funnel 13 and discharged through an outlet conduit 14. The conduit '8 from, the blower 7 to the classifier may be additionally provided with a nipple 15 for a supply of hot air or 'fresh air, and also with a nipple 16 for eliminating any excess amount of air.

Due to the provision of a number of suction conduits 10, six such conduits being employed in the illustrated embodiment, and due to the uniform distribution of the locations where these suction conduits communicate with the top of the grading chamber, the ascending air is forcefully subjected to a circulatory motion which results in the desired upward spiral of air motion to a considerably better extent than heretofore attainable in known air-circulation classifiers. While, if desired, a single cyclone may be connected in the common return conduit 12 between the classifier and the blower 7 in lieu of the individual cyclones of the illustrated embodiment, the provision of a separate, relatively small cyclone for each suction conduit has the advantage of reducing the overall diameter of the entire equipment.

It will be obvious to those skilled in the art, upon studying this disclosure, that my invention permits of a variety of modification in structural details and arrangement of components, thus embodying the invention in devices other than particularly illustrated and described herein, without departing from the essential features of my invention and within the scope of the claims annexed hereto.

I claim:

1. A classifier of the air-circulation type, comprising a housing defining in its upper portion a grading chamber having a height less than the overall height of said housing, a rotatable whirling plate located in the lower portion of said housing, a supply duct and a generally tubular guide structure located within said housing and communicating with said chamber above said plate for supplying the material to be classified, said housing having a discharge opening at its bottom for discharging separated coarse components of the material, external air circulation means comprising an *air inlet duct communicating with the bottom portion of said housing to pass an ascending air flow through said chamber, said circulation means having a plurality of suction ducts tangentially joined with said housing at the top portion of said chamber and distributed over its periphery for causing the ascending air flow to travel on helical paths in said chamber, and dust separtaor means with which said suction conduits are tangentially joined.

2. In a classifier according to claim 1, said lower portion of said housing comprising an inwardly tapering cone, said whirling plate being located Within said cone, said air circulation means comprising a blower outside said housing and having a single air conduit connecting said blower with all of said suction conduits.

3. A classifier of the air-circulation type, comprising a housing defining in its upper portion a grading chamber having a height less than the overall height of said housing, a rotatable whirling plate located in the lower portion of said housing, a supply duct and a generally tubular guide structure located Within said housing and communicating with said chamber above said plate for supplying the material to be classified, said housing having a discharge opening at its bottom for discharging separated coarse components of the material, external air circulation means comprising an air inlet duct communicating with the bottom portion of said housing to pass an ascending air flow through said chamber, said circulation means having a number of suction ducts tangentially joined with said housing at the top portion of said cham- 4 ber and distributed over its periphery for causing the ascending air flow to travel on helical paths in said chamber, a plurality of dust separator cyclones tangentially connected with said respective suction conduits and mounted at said housing and distributed along the periphery thereof, said cyclones having a common air outlet conduit, and blower means interposed between said common outlet conduit and said air inlet duct.

4. A classifier according to claim 1, said tubular guide structure coaxially surrounding said supply duct above said whirling plate in radially spaced relation to said supply duct, said guide structure and said supply duct each having a stationary upper portion and a telescopically movable lower portion, said movable lower portions of said guide structure and said supply duct being mutually fastened for being lowered and raised together with each other, said guide structure having an outer wall parallel to the inner wall of said housing whereby said grading chamber is formed between said housing wall and said guide-structure wall and has an annular shape of substantially uniform cross section long the height of the chamber.

5. In a classifier according to claim 4, said housing wall and said guide structure having a frusto-conical downwardly widening shape.

6. A classifier according to claim 4, including means for adjusting the height of said movable portions of said tubular guide structure and said supply duct relative to said whirling plate and relative to said housing.

References Cited in the file of this patent UNITED STATES PATENTS Watson Feb. 28, 1950 Gustavsson Jan. 26, 1960 OTHER REFERENCES 

1. A CLASSIFIER OF THE AIR-CIRCULATION TYPE, COMPRISING A HOUSING DEFINING IN ITS UPPER PORTION A GRADING CHAMBER HAVING A HEIGHT LESS THAN THE OVERALL HEIGHT OF SAID HOUSING, A ROTATABLE WHIRLING PLATE LOCATED IN THE LOWER PORTION OF SAID HOUSING, A SUPPLY DUCT AND A GENERALLY TUBULAR GUIDE STRUCTURE LOCATED WITHIN SAID HOUSING AND COMMUNICATING WITH SAID CHAMBER ABOVE SAID PLATE FOR SUPPLYING THE MATERIAL TO BE CLASSIFIED, SAID HOUSING HAVING A DISCHARGE OPENING AT ITS BOTTOM FOR DISCHARGING SEPARATED COARSE COMPONENTS OF THE MATERIAL, EXTERNAL AIR 